1. Field of the Invention
The present invention relates to an inkjet recording apparatus of ejecting a functional liquid material such as ink drop on a recording medium to record an image (including letters, hereinafter the same). More specifically, the present invention relates to an inkjet recording apparatus equipped with a head unit having a mechanism of suctioning ink mist generated at the ejection of an ink drop and suctioning also ink adhered to a nozzle plate (inkjet head).
2. Background Art
The inkjet recording apparatus where a functional material (functional liquid material) curable with energy such as ultraviolet ray and electron beam is ejected on a recording medium from nozzles of an inkjet head and the functional material is cured by the irradiation of energy, thereby performing the image formation, has many characteristic features, for example, this system is environment-friendly, high-speed recording can be made on various recording mediums and a high-definition image with less blurring is obtained. In particular, development of a recording apparatus using an ultraviolet curable functional material (ultraviolet curable ink) is proceeding in view of easy handling of light source, easy downsizing and the like.
The inkjet head has a large number of nozzles and when an ejection failure of the nozzle is generated, this is visible as an image defect. The ejection failure of nozzle occurs prominently in particular when ejection from the nozzles is continued for a certain period of time. The cause thereof includes misdirected ejection, no ejection, change of ejection amount and ink dripping, for which adhering ink attributable to ink mist and attached on the nozzle plate is responsible.
In order to prevent the ink from adhering on the nozzle plate, there is known an inkjet printer where wiping, suctioning or spitting of the nozzle surface is performed while the inkjet head is located off the recording region, or volatile substances of the ink adhered to the inkjet head are removed by blowing air to the inkjet head or suctioning air in the vicinity of the inkjet head (see, for example, JP-A-2005-14560 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”)). Also, there have been proposed an inkjet recording apparatus where a flexible duct having a recovery port nearly flush with the nozzle surface is provided as a separate body from the inkjet head and the ink mist is suctioned together with air from the recovery port (see, for example, JP-A-2005-205766), and an image forming apparatus where an air flow in a constant direction is created in a recording device by the blowing or suctioning of air and the ink mist is trapped by the air flow (see, for example, JP-A-2005-199465).
However, the recording devices described in JP-A-2005-14560, JP-A-2005-20576 G and JP-A-2005-199465 all are a recording apparatus employing a system such that the recording is performed by ejecting an ink while transferring an inkjet head in the direction perpendicular to the conveyance direction of a recording medium, and in the case of an inkjet recording apparatus employing a single pass system using a full line head of recording an image by only once passing a recording medium beneath the inkjet head, the wiping, suctioning or spitting of head surface cannot be performed, because the head is always located in the recording region.
In the recording apparatus described in JP-A-2005-14560, volatile substances adhered to the inkjet head are removed by generating an air flow in the vicinity of the inkjet head with use of air-blowing or suctioning means disposed apart from the inkjet head, but because of distant location from the head, the effect of removing nonvolatile substances is insufficient. Nonvolatile substances are gradually accumulated in the inkjet head during a long-term use and cause an ejection failure of nozzle.
When ink mist is removed by suctioning air in the vicinity of nozzles from somewhat distant position or by blowing and suctioning air as in the recording apparatus described in JP-A-2005-205766 and JP-A-2005-199465, this sometimes incurs deterioration of the straight ejection property of ink and reduction in the image quality. Also, it is difficult to completely prevent the ink mist from adhering to the nozzle plate, and when ink mist is once attached to the nozzle plate, there is no effective means to solve the ejection failure of nozzle, for example, the ink adhered during image drawing cannot be removed.